In search of dark energy: Observing the expanding universe with glass

In the heart of the Texas desert, an optical telescope is on a mission to spot the invisible. The Hobby-Eberly Telescope, located at The University of Texas McDonald Observatory, is the world’s third largest optical telescope, yet it’s currently undergoing modifications to look beyond the visible and uncover the unseen forces that expand our universe.

While Einstein’s Theory of Relativity concluded that the universe is static, Edwin Hubble discovered the opposite: The universe is expanding faster than we ever thought possible. The mysterious force that causes this expansion is still widely unknown — a force called dark energy.

Dark energy differs from dark matter, which is an unseen matter with gravitational pull that makes up 27 percent of the universe. Together, dark energy and dark matter make up about 95 percent of the universe (about 68 and 27 percent, respectively). Only about 5 percent of the universe is made up of normal matter — the stars, planets, and the gasses that we can more easily observe.

Since dark energy is so difficult to detect, researchers are using a mix of state-of-the-art computerized sensors and classic technologies in particle colliders, telescopes, and spectrometers to search for the answers behind this curious force.

The quest to discover dark energy

Today, the search for the origins of dark energy is taking scientists from subterranean tubes to mountaintops. The Large Hadron Collider serves as a key tool in the search for dark energy and matter. The collider, which restarted in April after two years of upgrades, crashes particles at near light speed to recreate the conditions that existed moments after the Big Bang. This research, scientists hope, will help explain more about dark energy and its creation.

But traditional telescopes also contribute to the search for clues about dark energy. The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) project combines the power of one of the world’s greatest optical telescopes with a new array of spectrographs in order to map the three-dimensional positions of one million galaxies. By mapping these galaxies, researchers can measure how fast the universe expanded over time, and use this information to clarify the nature of dark energy.

A clear picture of dark energy

Glass plays a key role in uncovering the far-reaching answers of space. At HETDEX, 156 state-of-the-art spectrographs will serve as the eyes into the universe’s distant past. These spectrometers, which are using main components made of BOROFLOAT glass — the floated borosilicate glass made by SCHOTT — will capture the full spectrum of light, measure the distances between galaxies at different times in the early universe, and reveal its composition. With those measurements, scientists can deduce the rate of the universe’s expansion and further understand the physics of dark energy.

BOROFLOAT’s exceptionally high transparency, outstanding visual quality and optical clarity, and its outstanding thermal resistance will be key performance features helping them to do so. For example, the low thermal expansion of this glass is crucial to the HETDEX project because the Hobby-Eberly Telescope, located more than 6,600 feet above sea level, experiences seasonal temperature and weather fluctuations throughout the year, including snow in the winter and plenty of hot Texas sunshine throughout the summer. BOROFLOAT resists the challenging expansion and contraction forces that such change of temperatures would typically cause, ensuring high resolution and consistency in researchers’ observation results.

Additionally, the glass boasts high chemical durability and excellent mechanical strength mainly due to the addition of higher amounts of boron oxide in its composition, which strengthens the chemical bonds within the glass network. The added boron oxide gives BOROFLOAT glass a low light refraction behavior, which, together with the material’s superior transmission, are key requirements for precise spectrometer measurement results. Light transmission in glasses will be significantly influenced by Fe2O3 impurity levels. BOROFLOAT glass is made of pure raw materials, resulting in an extremely low-iron impurity level for float glasses. The sum of it guarantees exceptionally high transmission values. In fact, BOROFLOAT is the industrial glass with the lowest level of iron impurity of all float glass materials in the market.

The HETDEX project holds the key to unlocking the secrets of the cosmos. Glass will serve as a significant material as researchers gaze into the earliest millennia in time to better understand the forces that continue to shape the universe.

Greetings, I’m Tina Gallo, Manager, Applications and Logistic Services for SCHOTT’s Home Tech division. My expertise is in material science, specializing in glass and glass-ceramic materials, but I also focus on new business development. With more than 18 years of experience in the specialty glass industry, I’ve served in a wide variety of engineering and managerial roles at SCHOTT in the U.S. and Germany. I’ve authored and co-authored eight patents and papers, one of which received the Dana Chase Award in 2003. I earned my master’s degree in material science from RWTH Aachen University in Germany. In my spare time, I enjoy coaching girls field hockey, hiking, and gardening.